Rotaviruses have been studied extensively in many parts of the world predominantly by cross-sectional approaches. Such studies have yielded essentially "numerator" data which indicated that rotaviruses are a major cause of diarrheal illness in infants and young children. There has been a paucity of longitudinal viral gastroenteritis studies that yield not only important "denominator" data but also valuable insights into the natural history of a pathogen or illness, with special emphasis on epidemiologic, immunologic and laboratory information. We, therefore, initiated an intensive examination of anal swab and serum specimens obtained during a previous LID long-term longitudinal study (1955-1969) at Junior Village, a welfare institution for homeless, but otherwise normal children. Anal swabs and blood specimens were obtained routinely from the youngest age groups, which ranged from 6 months to about 5 years of age during various periods of the study. Surveillance was carried out by a trained medical staff. Children were housed in cottages according to their age. Rectal temperatures were obtained on each child daily, routinely, a physician examined any child with a rectal temperature of 100.6 degrees F or greater. Careful medical records were kept by the nursing staff on all children. Thus, with this background, we plan to investigate the natural history of rotavirus infections in a longitudinal manner employing newly developed techniques such as serotyping of rotaviruses with VP7 specific monoclonal antibodies and determining the epitope-specific serologic response in sequential sera to determine the scope of homotypic and heterotypic responses. In addition with the availability of rotavirus strains obtained over 20 years ago, it is planned to compare such strains with current isolates at the genetic level.